Control of gas turbine engine

ABSTRACT

Systems, devices, and methods for controlling a fuel supply for a turbine or other engine using direct and/or indirect indications of power output and optionally one or more secondary control parameters.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 12/407,233, filed Mar. 19, 2009, the entire contents of whichare hereby incorporated by reference.

TECHNICAL FIELD

The application relates to the operation of turbine engines and, morespecifically, to methods and apparatus for control of the supply of fuelprovided to gas turbine engines using electronic engine control systems.

BACKGROUND

Many new aircraft engines, including both engines currently indevelopment and engines recently certified for flight use, employelectronic engine control systems. As well, older aircraft, designedbefore electronic control systems were common, are sometimes retrofittedwith such systems. Among other advantages, electronic engine controlsystems can help to reduce pilot workload, provide simpler and moreefficient interfaces with modem cockpit control systems, provideimproved protection for engines against extreme operating conditions,and enhance prognostic and diagnostic capabilities.

An important parameter to be controlled by an electronic enginecontroller in a turboprop or turboshaft engine is engine output power(or output torque). Such power is most often controlled through controlof the rate of fuel flow provided to the engine.

For measuring and reporting current engine power output, prior artengine controllers have typically employed mechanical transducers, suchas phase-shift torque meters. Such mechanical transducers, however,require space and add weight to an engine; the addition of either volumeor weight to engines is typically undesirable, particularly in aerospaceapplications. In a turboprop or turboshaft engine, for example, the useof such transducers can require modification of the reduction gearbox(RGB) and associated components.

SUMMARY

The disclosure provides, in various aspects, methods, systems, anddevices for controlling the supply of fuel to engines, includingparticularly aircraft-mounted turbine engines such as turboshafts orturboprops.

In various aspects, for example, the disclosure provides methods ofcontrolling such fuel supplies, the methods comprising steps ofmonitoring a differential oil pressure, such as the differentialpressure measured across the reduction gear box (RGB), associated withan operating engine, the differential engine oil pressure determinedusing signals representing at least two measured operating engine oilpressures, to determine whether a change in the monitored differentialengine oil pressure has occurred; upon determining that a change in themonitored differential engine oil pressure has occurred, using signalsrepresenting at least one other aircraft or engine operating parameterto determine whether the change in differential engine oil pressurecorresponds to a desired change in an output power level for the engine;and if it is determined that the change in differential engine oilpressure does not correspond to a desired change in an output powerlevel for the engine, calculating a desired fuel flow rate for theengine and either providing a corresponding command signal to an enginefuel supply controller or causing a current fuel flow rate to becontinued for a determined time interval.

In further aspects, the disclosure provides methods of controlling suchfuel supplies, in which the methods comprise monitoring a differentialoil pressure associated with an operating engine, the differentialengine oil pressure determined using signals representing at least twomeasured operating engine oil pressures, to determine a correspondingindicated engine output power level; monitoring at least one otheraircraft or engine operating parameter to determine whether theindicated engine output level corresponds to a desired output powerlevel for the engine; and if the indicated engine output level does notcorrespond to the desired output power level for the engine, calculatinga desired fuel flow rate for the engine and either providing acorresponding command signal to an engine fuel supply controller orcausing a current fuel flow rate to be continued for a determined timeinterval.

In further aspects the disclosure provides systems and devices,including controllers, for controlling the supply of fuel to suchengines according, for example, to such methods.

Further details of these and other aspects of the subject matter of thisapplication will be apparent from the detailed description and drawingsincluded below.

DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are illustrated in the figures of theaccompanying drawings, which are meant to be exemplary and not limiting,and in which like references are intended to refer to like orcorresponding parts.

FIG. 1 is a schematic diagram of a gas turbine engine comprising asystem for controlling a fuel supply for an aircraft-mounted turbineengine in accordance with the disclosure.

FIG. 2 is a schematic diagram of a differential oil pressure transducersuitable for use in implementing embodiments of systems and methods ofcontrolling a fuel supply for an aircraft-mounted turbine engine inaccordance with the disclosure.

FIG. 3 is a schematic diagram of an embodiment of a system forcontrolling a fuel supply for an aircraft-mounted turbine engine inaccordance with the disclosure.

FIGS. 4 and 5 are schematic flow diagrams of embodiments of processesfor controlling a fuel supply for an aircraft-mounted turbine engine inaccordance with the disclosure.

FIG. 6 is a representative plot of oil pressure and verticalacceleration versus time during a negative-g maneuver by an aircraft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various aspects of embodiments of systems, devices, and methods inaccordance with the disclosure are described through reference to thedrawings.

FIG. 1 is a schematic diagram of a system 100 for controlling a fuelsupply for an engine 200 in accordance with the disclosure.

In the example shown, turbine engine 200 is a turboprop engine suitablefor use in providing primary flight power for an aircraft. In theexample, engine 200 comprises a gas generator section 202 and a powermodule 212. Gas generator section 202 includes an accessory gearbox (notshown), a multi-stage compressor 206, a reverse-flow combustor 208, anda high pressure compressor turbine 210. In the example shown, powermodule 212 comprises power turbine 214 (which may be multi-stage) andreduction gearbox (RGB) 216 for stepping down the rotational speed ofturbine shaft 220 to a speed appropriate for a driving propeller shaft.

The operation and interactions of components 202-220 of engine 200 andother engines suitable for use in implementing systems, devices, andmethods according to the disclosure will be well understood by thoseskilled in the relevant arts. As will be further understood by thoseskilled in such arts, the systems and methods disclosed herein aresuitable for use in controlling fuel supplies for a wide variety of bothturbine and non-turbine engines in addition to those described herein.

In a gas turbine engine such as a turboprop engine 200 or a turboshaftengine, engine output power is generally dependent, among other factors,on the rotational speed of gas generator shaft 220. Control of the speedof a gas generator such as that of gas generator section 202, andtherefore gas generator shaft 220, of FIG. 1 can be accomplished byregulating the amount of fuel supplied to the combustion chamber (e.g.,combustor 208 of FIG. 1) in view of other factors such as altitude,inlet pressure, and inlet temperature.

In systems and methods according to the disclosure, the amount of fuelprovided to a combustor (or other fuel injection system), and therebythe engine output power, can be regulated by an electronic enginecontrol system (EEC 110) such as a Full-Authority Digital ElectronicControl (FADEC) system. Such EECs 110 can use anyone or more of a numberof parameters as input in determining the amount of fuel to be suppliedto the combustor in order to achieve or maintain a desired engine poweroutput. Examples of such parameters can include current output power,altitude, inlet and outlet air pressures, and inlet and outlet airtemperatures.

As shaft output power can be expressed as:

Shaft output power=(Shaft torque)×(propeller speed),

primary desirable factors in controlling fuel supply can includepropeller speed (Np) and parameters which are directly proportional toshaft torque, such as differential engine oil pressure measured acrossthe RGB in a turboprop and/or stress and/or strain in the shaft. Thusprimary input sources for use by EEC 110 in determining current ordesired output power, and thereby desired fuel flow, can include, forexample, phase-shift torque meters and/or differential oil pressurestransducers placed at, for example, the oil inlet and outlet of the RGBin a turboprop.

Thus, as described below, system 100 for controlling the fuel supply toengine 200, can comprise, among other components, one or more automaticdata processors (e.g. EECs) 110 and one or more sensors or other inputdevices 102, 104 for assessing and/or confirming engine output powerlevels, for calculating desired fuel flow rates for the engine 200, andfor issuing command signals to fuel pumps and/or other fuel controlcomponents 114 to cause such calculated desired fuel flow rates to beprovided to the engine.

Primary input sensor(s) 102 may be provided for acquiring signalsrepresenting engine output power or parameters useful in determiningengine output power. Such signals may represent direct measures ofoutput power (as for example in the case of phase-shift torquecontrollers, differential oil pressures, and or propeller speedindicators), or indirect measures, through measurement of parameterswhich may be used to deduce output power.

Input sensor(s) 104 can be provided to acquire data signals representingparameters relevant to engine operation or otherwise useful inconfirming the current output power; which, for example may beindirectly associated with engine performance, and/or used to confirmconditions in which an engine 200 is operating, and thereby to confirmthe meaning of output readings of one or more transducers 102, andthereby confirm current and desired engine output and fuel supplysettings. Examples of parameters readable by sensors 104 that can beused to confirm a primary engine power output indication can includevertical or other accelerations at the engine location, main oilpressure, which can for example be affected by aircraft accelerations,and/or the rotational speed Ng of the gas generator, e.g., section 202in FIG. 1. While main oil pressure and accelerometer readings can beused to acquire information regarding movement of the aircraft or othervehicle in which an engine is mounted, factors such as Ng can be use toconfirm whether in fact a significant change in engine operation hasoccurred.

In the example shown in FIG. 1, system 100 for controlling the fuelsupply of engine 200 comprises an engine output power transducer 102 inthe form of a differential oil pressure transducer 300 such as, forexample, that shown schematically in FIG. 2. As will be understood bythose skilled in the relevant arts, the differential oil pressuresprovided by transducer 102, 300 can be interpreted as providing a directmeasure of the output torque of engine 200, and therefore is directlyproportional to engine output power.

Operation of an embodiment of a fuel control system 100 in accordancewith the disclosure may be described in conjunction with such atransducer 102, 300. Those skilled in the relevant arts, however, willunderstand that phase-shift torque meters and other direct measures ofengine torque can be used as input sources 102.

In the embodiment shown in FIGS. 1 and 2, differential oil pressuretransducer 102, 300 can be disposed proximate a first stage reductiongear 224 of RGB 216, and can comprise a ring gear 302, cylinder 304,piston 306 connected to valve 310, and spring 312. Rotation of ring gear302 can be resisted by helical splines, which can impart an axialmovement of the ring gear and to piston 306. Movement of piston 306 cancause valve 310 to move against spring 312, opening a valve orifice andallowing flow of pressurized oil into torque pressure chamber 314.Movement of piston 306 can continue until the pressure of oil in chamber314 is proportional to the torque being transmitted to ring gear 302.Because external pressure can vary and can affect the total pressureapplied to piston 306, the internal RGB static pressure applied atchamber 316 can be applied to the reverse side of piston 306, resultingin measurement of differential oil pressure in the RGB 216. This RGBdifferential pressure can be interpreted as a measure of torque appliedto output shaft 218 by the RGB 216, and therefore can be used as acontrol parameter in determining and controlling the amount of fuelsupplied to engine 200.

As will be understood by those skilled in the relevant arts, transducers102, including any transducers 300, can be of any suitable form foraccomplishing the purposes described herein; the arrangement shown inFIG. 2 is merely an exemplary embodiment of a single type of transducerthat can be used in implementing the methods, systems, and devicesdisclosed herein.

FIG. 3 is a schematic diagram of a system 100 for controlling a fuelsupply for an aircraft-mounted turbine engine in accordance with thedisclosure. System 100 is suitable for use, for example, in controllinga fuel supply for an engine such as that shown at 200 in FIG. 1. System100 comprises one or more sensors 102 for reading and transducing engineoperating parameters such as, for example, differential oil pressure(see, for example, sensor 300 of FIGS. 1 and 2), propeller speed Np, andshaft torque (not shown). System 100 can further comprise one or moresensors 104 for reading and transducing other parameters associated withoperation of the engine 200, such as, for example, inter-turbinetemperature ITT, engine inlet temperature T1, main oil pressure MOP, andmain oil temperature MOT; and other parameters such as power supplyoutput 386, relay status 388, A/C discretes 390, cockpit power controllever (e.g., power control lever rotary variable differentialtransformer PCL RVDT 392), and other avionics devices 394. One or morecommunications channels 106, 108, such as digital buses, electronicengine controls (EECs) 110, 110′ and fuel control units (FCUs) 114 arealso provided. In the embodiment shown, redundant EECs 110, 110′ areprovided.

As will be understood by those skilled in the relevant arts, the variouscomponents of system 100 may be implemented, separately or jointly, inany form or forms suitable for use in implementing the systems, devices,and methods disclosed herein. For example, sensors 102, 104 for readingand transducing engine operating parameters such as differential oilpressure, shaft stress and/or strain, compressor inlet pressure,propeller speed Np, inter turbine temperature ITT, compressor inlettemperature T1 or outlet temperature, main oil pressure MOP, and/or mainoil temperature MOT may be of any mechanical, hydraulic, electrical,magnetic, analog and/or digital compatible form(s) suitable for use inimplementing desired embodiments of the systems, devices, and methodsdisclosed. For example, as suggested by FIG. 2, a pressure transducersuch as differential oil pressure transducer 300 may providemechanical/visual output for full or partial manual control of a turbineengine; in other embodiments, temperature, pressure, or other sensorsproviding digital and/or analog electromagnetic and/or mechanicalsignals representing the measured parameters may be used. Many suitabletypes of transducers are now known; doubtless others will be developedhereafter.

Selection of suitable sensors, transducers, and/or other devices formonitoring values of parameters 104 will depend, among other factorssuch as cost, weight, etc., on the nature of the parameters to bemonitored; such selection will be well within the scope of those havingordinary skill in the art, once they have been made familiar with thisdisclosure.

Communications channels 106, 108, such as those between sensors 102, 104and EEC/processor 110 can comprise any single or redundantcommunications devices or systems, including for example dedicated,direct-wire connections, serial or parallel buses, and/or wireless datacommunications components, suitable for accomplishing the purposesdescribed herein. As will be understood by those skilled in the relevantarts, it can be desirable in some applications, particularly aerospaceapplications, to provide sensors 102, 104, communications channels 106,108, processors 110, and fuel control units (FCUs) 114 in redundantsets, particularly with respect to devices which generate, transmit, orprocess electrical signals. It can further be desirable to provideinsulators, firewalls, and other protective devices between componentsof systems 100, and particularly redundant components, so as to precludemultiple failures. Even where a single housing is provided, as in thecase for a housing for a differential oil pressure transducer 300,multiple redundant sensors may be provided.

FCU 114 can comprise any relays, switches, and controls, and/or othercomponents, such as pump and/or valve controls, required to control fuelsupply at the command of EEC(s) 110, as for example by receiving andappropriately responding to command signals provided by EEC andconfigured to provide a desired fuel flow to engine 200. Such componentsand the use of them in implementing the systems and methods disclosedherein will not trouble those of ordinary skill in the art, once theyhave been made familiar with this disclosure.

EECs 110 may comprise any single, multiple, combination, and/orredundant general or special purpose data processors, such as printedintegrated circuit boards and associated or auxiliary components such asvolatile and/or persistent data storage devices 111, relays, andinput/output devices, suitable for accomplishing the purposes describedherein. Such components may comprise any hardware and/or soft- orfirmware and data sets, suitable for use in implementing the systems,devices, and methods disclosed herein.

As one example, EEC software contained in the EEC 110 and executed inprocessors associated therewith may include filters to condition thedifferential oil pressure signal as required. Noise may be present inthe signal due to various phenomena that may appear in the signal atvarious frequencies. For example, since the differential pressure oiltransducer 300 is located above the RGB 216 in close proximity to thepropeller, the oil pressure transducer 300 may respond to the frequencywith which propeller blades pass the transducer. Pulses within thesignal related to such phenomena could easily be filtered via softwareto ensure the EEC is processing a true output power or torque signal.

A wide variety of suitable transducers, communications units, dataprocessors, memories, relays, communications devices, fuel controldevices, and other components are now available, and doubtless otherswill hereafter be developed. Those skilled in the relevant arts will notbe troubled by the selection of suitable components, once they have beenmade familiar with the contents of this disclosure.

FIGS. 4 and 5 are schematic flow diagrams of exemplary processes 400,500 for controlling a fuel supply for an aircraft-mounted turbine enginein accordance with the disclosure. Processes 400, 500 are suitable foruse, in conjunction with systems 100, in implementing controls for fuelsupplies for engines such as that shown at 200 in FIG. 1.

Process 400 depicts a process for controlling a fuel supply for aturbine or other engine using direct and/or indirect, or primary,indications of power output and optionally one or more secondary, orconfirmatory, control parameters according to embodiments of thedisclosure. At 402, a current value or level of power output of theengine 200 is determined. For example, a direct reading of power outputof shaft 218 can be determined using, for example, a mechanical meanssuch as a phase shift torque probe. Alternatively, a proportionalmeasure of power output, such as differential RGB oil pressure, may beemployed as a control parameter, in either case using one or more ofsensors 102 to provide signals representing any one or more of suchparameters to EEC(s) 110 (and 110′). For example, as shown at 402 adifferential oil pressure across an RGB may be obtained, using atransducer such as differential oil pressure transducer 102, 300 of FIG.2 to provide for processing by EEC(s) 110 and/or 110′, and optionallyfor long- or short term storage in one or more memories 111, a signalrepresentative of or otherwise useful in determining current poweroutput of the engine 200. EEC 110 may process such signals into any formsuitable for further processing in calculating a desired fuel flow rateand preparing any desired control command signals.

At 404 a determination may be made as to whether the power readingobtained or determined at 402 indicates that a change in power hasoccurred. For example, a primary reading of power output of shaft 218made at 402 can be compared with data representing a previous outputreading previously stored in persistent or volatile digital memory 111by EEC 110. From such comparison it can be determined, visually orautomatically, that power output is indicated to have increased ordecreased, or to be desired. A visual determination may be made, forexample, by providing suitable output signals EEC 110 to a cockpitdisplay for review by a pilot, who can, by repeatedly checking thedisplay, determine that a change in engine output power is indicated.For further example, a signal representing a second or subsequentdifferential engine oil pressure can be obtained, using asuitably-configured transducer, such as differential oil pressuretransducer 300 of FIG. 2, data processor 110, and volatile and/orpersistent data storage 111, and compared to one or morepreviously-acquired signals, using suitably programmed mathematicalalgorithms, to determine whether a change in the monitored differentialengine oil pressure is indicated to have occurred. Such informationmayor may not be communicated to a pilot of the aircraft by EEC 110,110′.

If at 404 it is determined that no change in engine power output isindicated, at 405, the process can return to 402. For example, in anembodiment using an automatic data processor control in an EEC, processcontrol can be returned to logic block 402 for one or more subsequentreadings of engine power output indicators, so that continual monitoringof engine power output can be maintained; at any pass through logicalblocks 402, 404, where a change in engine output power is indicated,control can proceed to block 406.

If at 404 it is indicated that a change in engine power output hasoccurred relative to one or more previous power readings, or if itdesired to confirm that in fact no change has occurred, at 406 datarepresenting a secondary, or confirmatory, power and/or fuel controlparameter may be acquired, for use in confirming that a change in powerhas actually occurred. Such secondary parameter reading(s) can be usedto affirm or contradict the change in power output indicated at 404.

For example, it is possible, under some circumstances, particularlywhere an indirect measure of power output is used, that an erroneouschange in power output may have been indicated at 404. For example,during certain maneuvers of an aircraft or other vehicle, such as azero-g or a negative-g aircraft operation (which may be encountered forexample during turbulence or in sudden descents), acceleration of oilwithin the oil tank may cause an incorrect oil pressure reading, which,if differential oil pressure is being used as an indicator of enginepower output, can result in an incorrect indication of a powerchange—either, for example, by indicating that a change has occurredwhen in fact none has, or by exaggerating or minimizing the indicationof a true power change. For example, in such circumstances oil may beaccelerated away from the bottom of the tank where the oil pump islocated, causing the oil pump to cavitate, with a consequent drop inMOP. Such a drop in MOP can in turn result in a loss of differential oilpressure which is not necessarily connected with a change in enginepower output. This is illustrated, for example, in FIG. 6, whichrepresents a plot of oil pressure and vertical acceleration versus timeduring a negative-g maneuver by an aircraft or other vehicle.

FIG. 6 illustrates the effect of vertical accelerations on a number ofparameters that can be used to confirm whether an indicated change inengine power output has in fact occurred. As may be seen in the Figure,factors such as main oil pressure (MOP) can be significantly correlatedwith vertical acceleration (NZ), and therefore can be useful as inconfirming whether an indicated power change might be erroneous, and infact indicate a change in vertical accelerations. Other factors, such asgas generator speed Ng (NG) are less strongly correlated to verticalacceleration, and therefore can be useful in confirming that in fact nochange in output power is likely to have taken place, despite anindication to the contrary. Those skilled in the relevant arts willunderstand that the utility of various operating parameters in verifyingengine performance will depend upon the construction of a particularvehicle, the operating conditions, and other factors. The identificationand use of many such factors should not present significantdifficulties, once such persons have been made familiar with thisdisclosure.

Thus where at 404 it is indicated that a change in engine power outputhas occurred relative to one or more previous power readings, at 406, asecondary power and/or fuel control parameter may be acquired, for usein confirming that a change in engine output power has actuallyoccurred, or has occurred at a desired level. This can be useful, forexample, when no change in power setting is desired, as for examplewhere a FADEC or other system is configured to provide a desiredconstant power output: to change power when, for example, in fact nochange is desired, or appropriate, and none has in fact taken place,could cause inconvenient and even dangerous changes in actual enginepower settings. It can also be useful where, for example, a desiredchange in engine power has been requested, but subsequent changes inaircraft operating conditions cause an apparent change in engine poweroutput that is not accurate.

As an example of the use of a secondary or confirmatory parameter toconfirm whether a change in engine power output has occurred, or hasoccurred within a desired limit, one or more signals 382 representingacceleration of one or more parts of the aircraft can be acquired andinterpreted, to determine whether the apparent power change determinedat 404, or any part of such apparent power change, is accurate. Forexample, signals representing acceleration of the aircraft at, forexample, the location of the engine may be obtained, or determined usingacceleration at one or more other points, transposed mathematically tothe location of the engine to determine whether the engine or any partof it is subject to acceleration that might cause an erroneous powerindication.

For example, one or more locations on the aircraft or other vehicle maybe equipped with one or more accelerometers 104, 382 (FIGS. 1,2), whichwould provide various components of aircraft vertical, horizontal, androtational acceleration to EEC 110 or other flight control computer.Such parameter(s) (possibly along with other air data parameters such asair speed and altitude) may in turn be communicated to the engine EECvia a data bus or other digital or analog communications means 106, 108.Again, such secondary parameter(s) may be used to determine whether achange in differential oil pressure detected at 404 is due to aircraftoperations rather than a change in output power.

In other embodiments, secondary parameter(s) obtained at 406 may includeinputs from other sensors 104, such as gas generator speed or interturbine temperature ITT. Engine power output may be calculated based onthese inputs using, for example, a digitized engine performance modulewithin software stored in or otherwise executed by the EEC 110. This maythen be compared to the power output determined at 402 and/or toprevious power output readings in order to determine whether a change inpower has occurred or is correctly indicated at 402.

It is also possible to use pilot-initiated control inputs as primary orsecondary indicators of desired power settings. For example, controlinput from PCL RVDT 104,392 can be used to indicate a desired outputsetting.

At 408 it is determined whether or not actual engine power output needsto be modified to meet current intended flight commands, and if so, towhat extent. For example, data signals representing actual power outputmay be compared to data signals representing desired power output, usingknown computer algorithms. It having been determined whether the powersetting indicated at 402 is correct or needs correction, control of theprocess 400 can be transferred to logic block 412.

As mentioned above, where it is determined at 408 that actual poweroutput requires correction, the power output can be modified byincreasing or decreasing the fuel flow f. At 412, the fuel flow frequired to compensate for any difference in indicated and desired orotherwise commanded power settings is calculated. As will be understoodby those skilled in the relevant arts, calculation of the desired f willdepend upon a number of factors, including the type and model of engineused, the type and model of aircraft or other vehicle in which it isinstalled, the operating conditions of the engine and vehicle, the typeof fuel used and its condition, and optionally others.

At 414, signals representing the calculated desired or required fuelflow f is output by the EEC system, for use, for example, in providingoutput command signals for a fuel pump or other device, and control ofprocess 400 can return to 402.

If it is determined at 408 that a change in power is not desired, thencontrol of the process 400 passes to logic block 410, at which thecurrent fuel flow f may be held constant for a fixed or other determinedtime interval (for example, ten seconds) and control of the process 400can returns to control block 402.

Where an erroneous change in power output had been detected at 404, thetime interval applied at 410 is preferably long enough to allow thesituation which caused the erroneous output power detection to pass, butin any case is preferably short enough to prevent the development ofother possibly detrimental changes in flight or other vehicleconditions. For example, in the event that a momentary loss or reductionof MOP is experienced, as mentioned above and shown in FIG. 6, and acorresponding loss of differential oil pressure also occurs, at 410 theengine fuel flow may be held for a predetermined period long enough togive both the MOP and the differential oil pressure a chance stabilize,so long as no danger to flight safety has a chance to arise. After thedesignated time interval has passed, if the MOP and differential oilpressure have not recovered (i.e. signaling some other issue such assensor failure), the engine power may be reduced, engine control may begoverned using another input parameter, such as gas generator speed orinter turbine temperature (ITT) and/or the aircraft may fly in adegraded mode. Alternatively, in addition to or in lieu of usingpredetermined intervals of fixed length, various parameters 102, 104 canbe monitored to determine when a condition giving rise to erroneouspower readings has abated, so that control can be resumed based onprimary power indication factors.

Suitable methods and algorithms for determining fixed or variable timeintervals for application at block 410 in holding current fuel flow fconstant are known, and their use will be within the scope of thoseskilled in the relevant arts, once they have been made familiar withthis disclosure.

FIG. 5 provides a schematic diagram of another embodiment, 500, of aprocess for controlling a fuel supply to a turbine or other engineaccording to the disclosure, suitable for implementation using systemsand devices disclosed herein, including for example engine 200 of FIG. 1and system 100 as described. Many of the individual process steps 502,504, etc., are similar in form and alternative to various steps ofprocess 400, and form, to some degree, corresponding parts of process500. Thus in many cases the description below details only thoseportions of process 500 which differ significantly from theircounterparts in process 400.

At 502, a current value or level of power output of the engine 200 isdetermined. For example, a direct reading of power output of shaft 218can be determined using, for example, a mechanical means such as a phaseshift torque probe. Alternatively, an indirect or proportional measureof power output may be employed as a surrogate control parameter using,for example, one or more of sensors 102 providing signals representinganyone or more of a number of parameters (as, for example, disclosedherein). For example, as shown at 402 a differential oil pressure acrossan RGB may be obtained, using a transducer such as differential oilpressure transducer 102, 300 of FIG. 2 to provide for processing byEEC(s) 110, 110′ and optionally for long- or short term storage in oneor more memories 111, a signal representative of or otherwise useful indetermining current power output of the engine 200. EEC(s) 110, 110′ mayprocess such signals into any form suitable for further processing incalculating a desired fuel flow rate and preparing any desired controlcommand signals.

At 504 an output signal representing a parameter useful in confirmingthe accuracy of the power output indication determined at 502 isobtained. For example, signals representing one or more additionalflight and/or engine operating conditions, including for exampleacceleration, altitude, temperature, or other parameters (as for exampledescribed herein), may be obtained, using for example one or moretransducers 104, and provided to EEC(s) 110, 110′.

At 506, using data acquired at 502, 504, EEC(s) 110,110′ can determinewhether the current fuel flow rate f is correct, in view of currentpower command settings obtained from, for example, power settings set bya pilot using a control input such as PCL RVDT 104, 390 or by anautomatic flight control system. For example, as described herein datarepresenting a differential oil pressure obtained at 502 is used byEEC(s) 110, 110′ executing suitably-configured power setting software,to determine a corresponding apparent engine power output; and thesecondary data acquired at 504 is used, as described herein, to confirmwhether the power setting determined using the value acquired at 502 iscorrect.

Once the actual power output determined by comparing the values acquiredat 502, 504 is determined, at 508 EEC 110 can compare the actual powersetting to command power settings indicated by cockpit controls or othersources, and as described herein a corresponding suitable fuel flow ratef may be determined and at 510 used to provide corresponding commandsignals to a fuel control unit 114 (FIG. 1) or other device.

If either at 506 the current fuel flow rate f is determined to becorrect or suitable output command signals have been provided at 510,control can return to 502 so that continuous or continual monitoring ofengine operating conditions may be maintained.

The above descriptions are meant to be exemplary only, and those skilledin the relevant arts will recognize that changes may be made to theembodiments described without departing from the scope of the subjectmatter disclosed. Still other modifications which fall within the scopeof the described subject matter will be apparent to those skilled in theart, in light of a review of this disclosure, and such modifications areintended to fall within the appended claims.

Unless specified herein, or inherently required by the processesthemselves, the order of steps shown in processes disclosed is notsignificant, and such order may be changed without departing from themeaning or scope of the disclosure.

1. A method of controlling a fuel supply for an aircraft-mounted turbineengine, the method comprising: monitoring a differential oil pressureassociated with an operating engine, the differential engine oilpressure determined using signals representing at least two measuredoperating engine oil pressures, to determine whether a change in themonitored differential engine oil pressure has occurred; upondetermining that a change in the monitored differential engine oilpressure has occurred, using signals representing at least one otheraircraft or engine operating parameter to determine whether the changein differential engine oil pressure corresponds to a desired change inan output power level for the engine; and if it is determined that thechange in differential engine oil pressure does not correspond to adesired change in an output power level for the engine, one of:calculating a desired fuel flow rate for the engine and providing acorresponding command signal to an engine fuel supply controller; andholding a current fuel flow rate to the engine for a determined timeinterval.
 2. The method of claim 1, wherein the at least one otheroperating parameter comprises an acceleration of at least one portion ofan aircraft.
 3. The method of claim 1, wherein the at least one otheraircraft of engine operating parameter comprises at least one of anengine operating temperature, and engine operating pressure, and airtemperature, and an air pressure.
 4. The method of claim 1, wherein thecorresponding command signal provided to an engine fuel supplycontroller comprises signals adapted to modify a rate of fuel flowprovided to the engine. 5-10. (canceled)
 11. A controller for a fuelsupply for an aircraft-mounted turbine engine, the controller adaptedto: receive from at least one transducer input signals representing adifferential engine oil pressure; receive from at least one othertransducer input signals representing at least one other aircraft orengine operating parameter; and using the input signals representing thedifferential engine oil pressure, determine whether a change in thedifferential engine oil pressure has occurred; using input signalsrepresenting the at least one operating parameter, determine whether thedetermined change in differential engine oil pressure corresponds to adesired change in an output power level for the engine; and upondetermining that the determined change in differential engine oilpressure does not correspond to a desired change in an output powerlevel for the engine, one of: calculate a desired fuel flow rate for theengine and provide a corresponding output signal useful for controllingan engine fuel supply; and hold a current fuel flow rate to the enginefor a determined time interval.
 12. The controller of claim 11, whereinthe at least one other transducer comprises an accelerometer.
 13. Thecontroller of claim 11, wherein the at least one other transducercomprises at least one of a temperature transducer, and a pressuretransducer.
 14. The controller of claim 11, wherein the correspondingoutput signal is adapted to modify a rate of fuel flow provided to anengine.
 15. (canceled)